This invention is directed to an elastic laminate material having an elastomeric element comprising at least two different elastomeric materials in series. In one embodiment, this invention is directed to an elastomeric element comprised of a high performance elastomer, for example LYCRA(copyright) polyurethane, and a lower performance elastomer, for example a metallocene-catalyzed polymer, in series. The elastomeric element exhibits high performance elastic properties at reduced material costs. In another embodiment, this invention is directed to a garment utilizing the elastomeric element to provide improved comfort, fit and appearance of the product.
Elastic laminates are useful in many personal care products including diapers and undergarments. High performance elastomers, such as Lycra(copyright) spandex, are particularly useful because the laminates produced using these elastomers provide good product fit over an extended use period. However, such high performance elastomers are expensive. Further, the Lycra(copyright) polyurethane type laminates may provide a feminine or ruffled appearance that does not provide a flat or smooth surface that is discreet and invisible underneath clothing. Lower performance elastomers, including metallocene-catalyzed olefin polymers, have also been useful because of their low cost and clothlike appearance. Unfortunately, these less expensive elastomers do not necessarily provide high performance elastic properties and the thermoplastic laminates produced with these elastomers do not typically provide a good fit over an extended use period. As a result, products using these elastomers exhibit waist sag and poor leg fit. Generally, there is a need for an elastic laminate for personal care products that provides high performance elastic properties at a low material cost.
Related art alters or modifies the decitex, elongation or strand spacing of elastic elements in order to vary the tension across elasticized regions. In the present invention, the elastic properties of different elastomers are utilized to provide an elastic band that can be xe2x80x9ctunedxe2x80x9d to any particular area of a given product. This invention combines the high performance elastic properties of more expensive elastomers, such as Lycra(copyright) polyurethane, with the less expensive, lower performance elastomers, such as metallocene-catalyzed olefin polymers, to provide a material with high performance elastic properties and improved comfort, fit and appearance at a reduced material cost.
The present invention is directed to a multi-segment elastomeric band and laminate material useful in personal care products. The elastic band comprises at least two elastomeric segments adjacent to each other and in series. These segments have different polymer construction with different chemistries, molecular weight distributions, densities, and/or geometries. The elastomeric materials of the band can be defined so that a high performance elastomer, for example LYCRA(copyright) polyurethane, is used sparingly in regions where needed and the remaining regions of the band can comprise a lower performance elastomer, for example a single-site or metallocene-catalyzed olefin polymer. As a result, an elastomeric band is produced having high performance elastic properties where needed, at a reduced material cost. In another preferred embodiment, an elastic band is provided in which a first elastomeric material is comprised of a single-site or metallocene-catalyzed polymer having a density less than about 0.89 g/cc, and a second elastomeric material adjacent to the first, is comprised of another elastomeric polymer.
The elastic band may be bonded to one or two nonwoven webs, preferably spunbonded, to provide a multi-segment elastic laminate material. The elastomeric materials may be in the form of an elastomeric nonwoven web, for example, a spunbonded web, a meltblown web, a bonded carded web, or a combination thereof; a filament array; a film or a foam; or a laminate including one or more of the foregoing. The elastomeric materials may be permeable or impermeable to moisture vapor and/or liquid water, or have specific permeabilities.
Elastic polymers suitable for preparing the elastomeric band include, without limitation, elastomers made from block copolymers such as polyurethanes, copolyetheresters, polyamide polyether block copolymers, ethylene vinyl acetates (EVA) and the like; including polyurethanes available from E.I. Du Pont de Nemours Co., under the trade name LYCRA(copyright) (also known as xe2x80x9cspandexxe2x80x9d); elastomeric styrene-butadiene copolymers including those known as KRATON(copyright) materials which are available from Shell Chemical Company of Houston, Tex.; tetrablock copolymers, including styrene-poly(ethylene-propylene) elastomeric block copolymers available from the Shell Chemical Company of Houston, Tex. under the trade designation KRATON(copyright); polyamides, including polyether block amides available from Ato Chemical Company, under the trade name PEBAX(copyright); polyesters, such as those available from E.I. Du Pont de Nemours Co., under the trade name HYTREL(copyright); single-site or metallocene-catalyzed polymers, including single-site or metallocene-catalyzed polyolefins having a density less than about 0.89 grams/cc available from Dow Chemical Co. under the trade name AFFINITY(copyright); and natural and synthetic rubbers.
The adjacent elastomeric materials may be connected with a layer of adhesive, or by another bonding process known in the art, such as thermal bonding, ultrasonic bonding, chemical crosslinking, and mechanical lamination. The adjacent materials may be bonded together at edges which overlap each other. The elastomeric band can be elongated and bonded to an upper sheet and/or a lower sheet using any of the foregoing bonding technologies, to form the multi-segment elastic laminate. The resulting laminate exhibits hybrid properties of the adjacent elastomeric materials.
With the foregoing in mind, it is a feature and advantage of this invention to provide an elastomeric band and an elastic laminate material having high performance elastic properties and a more clothlike appearance while reducing material cost.
It is also a feature and advantage of this invention to provide a garment with improved fit, comfort and appearance having an elastomeric band comprising at least two different elastomeric materials adjacent to each other.